Outlook 2013 (Desktop) keeps disabling iCloud Outlook Add-in

I have been successfully using the iCloud Outlook Add-in for a few years now. A few days ago, however, I have noticed that the Add-in is automatically disabled every time I open Outlook. If I go to "File", "Options" "Add-ins", I find the iCloud Add-in check box is clear and that the add-in is disabled. If I enable the add-in, all is fine and the data I sync with in iCloud is visible and gets updated as it should. The next time I run Outlook after closing it (irrespective of whether or not I shut down or re-boot my PC) the add-in has once again been disabled. Any ideas as to what's up?

You should get a warning message "Addin problem ...." with a "View disabled addins" button at the right end. Click the button. In the Disabled Addins dialog there should be the option to always enable the addin.

@Joe: That's the problem, there is only an option to enable or disable. Nothing "permanent". Each time I close Outlook, the add-in is disabled when I re-open the program. The add-in is indicated as "unloaded" and does not offer the option of "load at startup" for some strange reason.

@JoeP517: The error message does not appear. The add-in is simply disabled every time I open Outlook. Once I re-enable it via "Options" and "Add-ins" it loads and works exactly as expected; until I close Outlook. Then the whole annoying saga begins again. This SEEMS to have started since the last batch of Office updates. (I'm trying to avoid uninstalling them one by one(!) in order to try to solve this issue).

@JoeP517: Agreed. I (thank heavens!!) made a full system backup; and saved a copy of my .pst file on the desktop; uninstalled the iCloud add-in; re-installed it (it corrupted everything in Outlook and in my iCloud "Cloud storage" AND on my iPhone; AND would not link Outlook to iCloud, or enable any syncing. After a few hours of serious perspiration, I deleted all contacts, calendars and tasks in Outlook and in iCloud's "Cloud"; an don my iPhone. I then imported my calendars, contacts and tasks from a saved copy of the outlook .pst file ... and hey presto! all worked again, full syncing and iPhone updated and synced as well. Then I closed Outlook ...re-opened it, and ... the add-in had been disabled AGAIN. I enabled it, and all worked well again. So, after all that I am back where I started. It seems I must enable the add-in via files, options every time I open Outlook. Very frustrating after several years of perfect use with the add-in.

@JoeP517: Many thanks, Joe. I tried the solutions in the posts under your kindly-provided link, and ended up with the same disaster as in my post #11 above! Fortunately I had learnt (the hard way) how to get back all of my data! So for now, I am simply re-enabling the add-in every time I open Outlook. I suppose this is not too much of a hassle, since I tend to leave Outlook open when I put my computer to sleep at the end of a session. Many thanks for your assistance, it is very much appreciated.

@JoeP517: Thank you for the link to the iCloud forum. I have posted the details of my dilemma there, and will wait and see if anything useful comes up. (I note that others have had similar problems, but not precisely the same as mine). In the mean time, I think I will let sleeping dogs lie and manually enable the add-in on the few occasions that I reboot my PC.